Elimination and rearrangement reactions in the electron impact ionization mass spectrometry of 2,4,5,5-tetrasubstituted 1,2,4-triazolidine-3-thiones

The electron impact mass spectra of 2,4,5,5-tetrasubstituted l,2,4-triazolidine-3-thiones exhibited, in addition to four main routes of fragmentation, a reaction leading to the formation of 5-alkyl-l,2,4-triazoline-3-thiones via an elimination of HR⁴ (R³ ≤ R⁴ are the substituents at C(5)) or via a McLafferty-type reaction from the rearranged molecular ion in the case of the 5,5-spiro derivatives. Substitution at N(2), N(4) and/or C(5) had a decisive effect on the contribution of the alternative reaction routes. Some fragments via the triazoline-thione structure were also formed.